MORPHOLOGIC CHANGES DURING FOLLOW-UP AFTER SUCCESSFUL PERCUTANEOUS TRANSLUMINAL CORONARY BALLOON ANGIOPLASTY - QUANTITATIVE ANGIOGRAPHIC ANALYSIS IN 778 LESIONS - FURTHER EVIDENCE FOR THE RESTENOSIS PARADOX

The purpose of this study was to determine if there are any morphologi c characteristics of lesions that renarrow (that is, restenotic lesion s) following successful coronary balloon angioplasty that are differen t from their appearance pretreatment or from the appearance of nonrest enotic lesions that might provide some new insight into the restenosis phenomenon. The study population consisted of 653 patients (778 lesio ns) with 6 months of angiographic follow-up (94% angiographic follow-u p rate) who were participating in the Multicenter European Research tr ial with Cilazapril after Angioplasty to prevent Transluminal coronary Obstruction and Restenosis (MERCATOR) study. Detailed quantitative an giographic measurements, including the mean diameter of the vessel seg ment (in millimeters) that was subjected to balloon dilation, were per formed preangioplasty, postangioplasty, and at follow-up using the car diovascular angiographic analysis system to provide some objective mea surement of the actual extent of luminal changes in the months followi ng coronary balloon angioplasty. Two different approaches for restenos is were used: (1) static criterion of >50% diameter stenosis at follow -up and (2) dynamic criteria of greater than or equal to 0.40 or great er than or equal to 0.72 mm change in minimal lumen diameter between p ostangioplasty and follow-up. Both approaches identified more severe s tenosis to be a typical feature for restenotic lesions before angiopla sty compared with nonrestenotic lesions. No differences were observed in lesion length, balloon-inflated vessel segment, or roughness index before angioplasty between the groups. Conflicting data were found for the amount of atherosclerotic plaque, symmetry index, and curvature i ndex. The restenotic lesion at follow-up compared with its initial app earance gave conflicting results depending on which approach was used. The dynamic criteria illustrate that the reference diameter and the m ean diameter of the entire segment dilated are reduced during follow-u p. Two messages emerge from the study: (1) the restenosis process clea rly involves the apparent normal vessel wall adjacent to the actual le sion, probably in response to the unavoidable injury caused by balloon dilatation and (2) the use of percentage diameter stenosis measuremen ts depending on the assumptions of normality for a reference segment w ill therefore underestimate the true extent of the restenosis process and should be replaced in clinical angiographic studies by absolute lu minal measurements.